Some of the best amateur radio publications are available from the Amateur Radio Relay League (ARRL). Most of the books that ARRL sells--on various aspects of the amateur radio hobby--relate well to other HF radio services. In addition, the ARRL also produces one of the best amateur radio magazines, QST.
Another publisher of technical books is TAB/McGraw-Hill. In addition to selling a number of beginner-, intermediate-, and advanced-level books on electronics, shortwave, and computers, the company also offers one of the best antenna books available. Joe Carr's Practical Antenna Handbook (2nd Edition) covers almost every practical antenna design with a down-to-earth approach.
Two excellent annual guides to HF/shortwave broadcast listening are available. The World Radio TV Handbook features hundreds of pages of frequency listings, addresses, transmitter sites for AM, HF/shortwave, and television broadcast stations around the world. For more information, write to: WRTH, BPI Communications, 1515 Broadway, New York, NY 10036.
The Passport to World Band Radio covers the same general topics as the WRTH, but it features less raw information and more interpretations of information and trends in international broadcasting. For more information, write to: Passport to World Band Radio, IBS, Box 300, Penn's Park, PA 18943.
Whether or not you are interested in HF/shortwave broadcasting, either of these books is invaluable if you need to discover which Latin American stations are fading into the 6200 kHz area marine frequencies or which African broadcasters are booming into the 40-meter amateur band.
For more up-to-date information on the propagational conditions, you can listen to radio stations WWV and WWVH, which are the two time- and frequency-standard stations for the United States. Both of these stations broadcast only time pips and the tone at the top the minute, along with announcements. WWV and WWVH are set to an atomic clock that ensures that they are exactly on time. Being a frequency standard means that the stations are exactly on frequency, and they can be used to calibrate transceivers or frequency counters.
WWV (from Ft. Collins, Colorado) and WWVH (from Kauai, Hawaii) both broadcast on 2500, 5000, 10000, and 15000 kHz. WWV also broadcasts on 20000 kHz. The two broadcasts are exactly the same, except that WWV features a male announcer for the time checks and WWVH airs a female announcer.
Hourly (at 18 minutes past the hour on WWV and 45 minutes past the hour on WWVH), the stations broadcast propagation reports. These reports are updated daily between 2100 and 2200 UTC (abbreviation for Coordinated Universal Time--Greenwich Mean Time) and they are the most up-to-date information that is available. WWV and WWVH broadcast information about three different propagational factors: A index, K index, Solar Flux. The A index and K index are related values that reflect the amount of geomagnetic activity in the ionosphere. The lower the numbers, the quieter the conditions are; the higher the number are, the more stormy the ionospheric conditions are. If the A and K indexes are very low (0-10 for the A and 0-3 for the K), the propagation should be better.
The last of the announced WWV/WWVH propagation conditions is the solar flux. The solar flux is directly proportional to the sunspot number, so the higher solar flux number (which would occur near the peak of the sunspot cycle) the better the propagation on frequencies above 10000 kHz.